In the past, a hot rolling apparatus, which performs the hot rolling of a workpiece such as a steel plate, has included a roughing mill and a finishing mill, and has further included a heating furnace or a heat-retaining/heating furnace, a shearing machine, a winding machine, and the like.
The above-mentioned hot rolling apparatus, first, heats a workpiece by a heating furnace. Then, the hot rolling apparatus performs the rough rolling of the workpiece by a roughing mill, conveys the workpiece while reheating the workpiece and retaining the heat of the workpiece by the heat-retaining/heating furnace, cuts front and rear ends of the workpiece by a shearing machine, performs the finish rolling of the workpiece by a finishing mill, and winds the workpiece using a winding machine.
Meanwhile, the conveying roller in the heat-retaining/heating furnace is made of heat-resistant steel so as to withstand high temperatures.
However, since deformation, such as wave or warpage, occurs at (particularly, a front end portion of) the workpiece that has been subject to the rough rolling, the conveying rollers in the heat-retaining/heating furnace receive an impact from the workpiece.
For this reason, the internal temperature of the heat-retaining/heating furnace is set so that the strength of the conveying roller does not deteriorate. Further, the conveying speed of the workpiece in the heat-retaining/heating furnace is set so that an impact exceeding an impact capable of being withstood by the conveying roller is not applied to the conveying roller. Specifically, the internal temperature is set to 1000° C. or less and the conveying speed is set to about 100 m/minute.    [Patent Citation 1] Japanese Unexamined Patent Application, First Publication No. H07-88528